Field of the Invention
This invention relates to a clock tuning and measuring system and, more particularly, to a clock tuning system in which the delay is automatically adjusted to provide the arrival of the clock pulse at an automatically selected clock path at the right time and to provide an arrangement whereby the arrival time of a clock pulse on a pre-selected path can be automatically measured.
In data processing systems the timing of events is extremely critical. The clock pulses which trigger these events must arrive at the prescribed time. It is known that circuits and especially transmission lines have inherent delay and accordingly, a clock pulse transmitted a long distance over such lines must be retimed. This has been done heretofore in data processing equipment by providing adjustable delays in the transmission lines such that the clock signal can be retimed. The retiming is accomplished by attaching an oscilloscope at the node where the clock pulse is to be retimed. The actual time of arrival of the clock pulse is compared with the required time of arrival and the delay adjusted manually accordingly. It will be appreciated that a number of these tuning points are required in data processing equipment. Accordingly, a big time and cost factor in the manufacture of data processing systems is the tuning of the system both when it leaves the factory as well as when it is installed in the customer's office. Along with the miniaturization of data processing equipment, it has become more and more difficult to scope the nodes where the timing is to be measured. This type of manual tuning has become virtually impossible with the advent of large scale integration, and particularly with encapsulated type circuits.